Jethro Tull is an ItSaul Plants cross between Coreopsis 'Zamfir' and Coreopsis 'Early Sunrise'. The vibrant golden yellow bloom is a single row of fluted flowers that blooms heavily in April, May and June. Jethro Tull is a great addition to any sunny perennial garden. A mass planting of Jethro Tull is an impressive sight.